Sub‐glass‐transition temperature interface formation between an immiscible glass rubber pair

Abstract We used neutron reflectivity to measure the interfacial width in the immiscible system polystyrene/poly( n ‐butyl methacrylate) (PS/P n BMA). Measurements were made on the same samples at temperatures ranging from below the glass‐transition temperature ( T g ) of PS to slightly above. We observed significant broadening of the interface at temperatures below the T g of PS, indicating chain mobility below the bulk T g value. The interfacial width exhibited a plateau at a value of 20 Å in the temperature range of 365 K < T < 377 K. A control experiment involving hydrogenated and deuterated PS films (hPS/dPS) showed no such broadening over the same temperature region. The results are consistent with a reduction of the T g of PS in the interfacial region of ∼20 K. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2664–2670, 2001